A radio wave sensor for sensing a sensing object such as a human body, etc., may be provided in a toilet seat apparatus that is placed and used on a toilet. In such a case, the radio wave sensor may be provided in the interior of a main part of the toilet seat apparatus mounted at the rear upper part of the toilet.
When a radio wave is radiated from the radio wave sensor provided in the interior of the main part, the radio wave passes through the toilet seat, etc., and propagates frontward. At this time, the radio wave is refracted by the toilet seat, etc.; the travel direction of the radio wave is changed; and there is a possibility that the sensing precision of the sensing object may decrease.